The present invention relates to jet drop recording systems, and more particularly to a composition for cleaning residual ink and any foreign particles from the orifices, fluid manifold, and fluid lines in an ink jet recorder.
Jet drop recording systems typically operate by pumping a liquid coating material such as ink under pressure to a manifold communicating with a series of small diameter orifices. As the coating material is ejected through the orifices under pressure, it forms fine filaments of coating material which break down into a series of discrete drops. At the point where the drops break from the filaments they pass through charging rings which, depending upon the pattern of coating material desired on a receiving member conveyed beneath the drop generator, either charge or do not charge every drop of coating material.
An electrostatic deflecting field is set up downstream of the charge rings and all drops which receive a charge are deflected from their trajectory by the deflecting field. A catcher is also associated with the system to catch those drops which it is desired to prevent from reaching the receiving member. In this manner, a predetermined pattern of drops will print upon the receiving member.
In many jet drop printing systems there are several hundred orifices having diameters ranging from about 0.0007 inches to 0.003 inches in diameter through which ink is forced. As can be appreciated when working with such small openings, formation of absolutely straight ink drop streams precisely aligned to pass through the charge rings and deflection field is critical. When dried ink or other foreign particles accumulate on the walls of the orifice or in other parts of the system such as in the fluid manifold or fluid supply lines, ink jet straightness is adversely affected, which in turn adversely affects the quality of printing of the system. These crooked jets may be caused by obstructions in the orifices which knock the ink jet streams off line or by a pressure drop in the system which causes the jets to wander.
Accordingly, these jet drop recorder systems have had to be cleaned periodically, either prior to or after use, to remove any dried ink, foreign particles, dust, soil, or the like. Prior art cleaning techniques have used either blasts of air, water, or a mixture of water and denatured alcohol to remove the accumulated particles and dust from the system. For example, both Stoneburner, U.S. Pat. No. 3,891,121, and Paranjpe, U.S. Pat. No. 4,031,561, teach use of a flushing fluid during startup of a jet drop recording system consisting of an equal mix of water and alcohol. However, such prior art cleaning techniques have not proved entirely satisfactory. Although most jet printing inks are aqueous based, they are formulated to become water insoluble when dry. Water alone, or a water-alcohol mixture will not wet the dried ink and other foreign particles which accumulate in jet drop recording systems. Moreover, particles which have become electrostatically charged and adhere to the internal walls of the system cannot easily be removed by water alone.
Although various general purpose cleaning solutions are available commercially, they have one or more shortcomings which render them unacceptable for use in jet drop printing systems. Among these shortcomings are problems with foaming, high viscosity, the presence of ammonia or other chemicals incompatible with the ink and mechanical components of the system, and a tendency of form films or leave residues on surfaces. As can be seen, the need exists in the art for a cleaning composition which can effectively remove dried ink, dust, soil, and other foreign particles from an ink jet recording system and yet be compatible with the materials in the system.